As an external storage device of a computer, an optical disc drive has several advantages such as large capacity and high speed access. The use of a CD-ROM [or CD-I (CD-Interactive)] drive and an MO (magnetooptic disc as one of erasable discs) is rapidly spreading. As a device other than those drives, an MD (minidisc; erasable disc) having a disc diameter of 2.5 inches has also been proposed. Further, a DVD (Digital Video Disc) is also being developed as a video storage medium.
The DVD is a recordable/reproducible optical disc like a read only disc, MO disc, or phase change type disc having the same diameter as that of a CD and is a disc in which video information compressed by an MPEG or the like can be reproduced or recorded/reproduced. In a DVD, the recording density is improved by improvements in digital modulation and an error correction coding together with the advancement of a short wavelength of a laser beam and the increase in NA of an objective lens. Even in the case of a single-layer disc, a data storage capacity is extremely large to be about 3.7 Gbytes. In a manner similar to that the CD and MD have initially been developed as digital audio discs and are also subsequently used as an external storage medium of a computer, it is also expected that the DVD of a larger capacity is used as an external storage medium of a computer.
It is considered that data read out from the CD-ROM and data from a hard disc drive are recorded by using a storage medium of a large capacity such as a DVD or the like. Hitherto, in case of the external storage medium of the computer, since a sector size (512 bytes, 2 kbytes, etc.) of 128 bytes.times.2.sup.i is a main stream, the data of the CD-ROM is also ordinarily recorded by such a sector size.
Upon recording/reproduction of data, a reliability (magnitude of an error rate) of the data is peculiar to the recording medium and the operation to select processes upon recording in consideration of it is not performed. In case of data in which a high reliability is required, however, it is necessary to further perform a protection by an error correction code upon recording. Thus, a redundancy of data increases and a recording capacity substantially decreases. Even when a significance of data is high, it is also necessary to strongly take a countermeasure for errors. Further, as in case of the CD-ROM, since there is a possibility such that data to be recorded has a plurality of formats (called modes), it is desirable to take a countermeasure for the errors in consideration of the formats.
It is, therefore, an object of the invention to provide a data recording apparatus and method and a data reproducing apparatus which can change a recording process in accordance with a reliability of data or the like.